Multi-strand electrical conductor

ABSTRACT

A light-weight electrical conductor comprising a plurality of at least seven longitudinally extending and closely wound strands, some of the wound strands being formed substantially of copper and the remaining strands being formed substantially of an electrically conductive grade of aluminum. Each of the strands in the conductor has an exterior surface coating of an identical electrically conductive material, preferably taken from the group of silver, nickel or tin. The conductor includes a suitable insulating material such as Teflon or the like which forms an outer cover layer for the conductor. Preferably, the conductor includes either seven or nineteen strands, the seven-strand conductor having three strands formed substantially of aluminum and the remaining four strands formed substantially of copper, and the nineteen-strand conductor having seven centrally located strands formed substantially of aluminum and twelve peripherally disposed strands formed substantially of copper.

United States Patent [15] 3,683,103 Mancino [4 1 Aug. 8, 1972 s41 MULTI-STRAND ELECTRICAL Primary Examiner-E. A. Goldberg CONDUCTOR Attorney-Channing L. Richard et al. [72] Inventor: John J. Mancino, Charlotte, NC.

[73] Assignee: J & J Equity Company, Charlotte,

Filed: July 7, 1971 Appl. No.: 160,362

US. Cl. ..l74/ll9 C, 174/126 CP Int. Cl. ..H0lb 5/08 Field of Search ..l74/l 19 R, 119 C, 126 CP, 84

[ ABSTRACT A light-weight electrical conductor comprising a plurality of at least seven longitudinally extending and closely wound strands, some of the wound strands being formed substantially of copper and the remaining strands being formed substantially of an electrically conductive grade of aluminum. Each of the strands in the conductor has an exterior surface coating of an identical electrically conductive material, preferably taken from the group of silver, nickel or tin. The conductor includes a suitable insulating material such as Teflon or the like which forms an outer cover layer for the conductor. Preferably, the conductor includes either seven or nineteen strands, the seven-strand conductor having three strands formed substantially of aluminum and the remaining four strands formed substantially of copper, and the nineteen-strand conductor having seven centrally located strands formed substantially of aluminum and twelve peripherally disposed strands formed substantially of copper.

9 Claims, 6 Drawing Figures PATENTEDAU: 8 I972 1 MULTI-STRAND ELECTRICAL CONDUCTOR BACKGROUND OF THE INVENTION.

Multi-strand electrical conductors are, quite obviously, designed primarily to provide a maximum current-carrying capacity, but the wide variety of different applications in which such electrical conductors are used frequently necessitates the use of materials which compromise somewhat the current-carrying capacity of the electrical conductors in an effort to satisfy other demands made upon the electrical conductor because of its particular application.

For example, in US. Pat. No. 3,261,908, issued July 19, 1966, there is proposed an electrical conductor designed as a power frequency transmission line which requires conductivity as well as a relatively high strength to weight ratio, and these requirements are met by employing different grades of aluminum for the interior and exterior strands of the electrical conductor. It is to be particularly noted, however, that the patentee accepts the reduced current-carrying capacity of aluminum rather than combining aluminum strands with strands of more conductive material (i.e., copper) because of the problems which such a combination would present such as corrosion occasioned by galvanic action between current-carrying strands of different materials.

' Additionally, it has been proposed in US. Pat. No. 3,345,456, issued Oct. 3, 1967, that steel strands be employed with a matrix and outer covering formed of copper to form a cable having high tensile strength so as to be suitable for use as a combined aircraft antenna and target tow line. In this patent, two dissimilar metals are employed, but the corrosive effect resultingfrom galvanic action is not considered by the patentee, no doubt because the electrical current carried by an antenna is insignificant in terms of causing any appreciable galvanic action between the dissimilar metal strands.

In the aerospace industry, there is a demand for electrical conductors which have a substantialcurrent-carrying capacity, which are extremely light weight, and which will have a long and reliable service life without deterioration as a result of galvanic action. Neither of the above-described prior artdisclosures, or any other prior art disclosure of which I am aware, provides an electrical conductor which can effectively combine highly conductive copper strands with aluminum strands in a proper combination which will carry significant amounts of current without the deteriorating effect of galvanic action.

SUMMARY OF THE INVENTION In accordance with the present invention, a lightweight electrical conductor is provided which comprises at least seven longitudinally extending and closely wound strands. Some of the strands are formed substantially of copper to provide maximum electrical conductivity, and the remaining strands are formed substantially of an electrically conductive grade of aluminum to reduce the overall weight of the conductor while increasing its strength. All of the closely wound strands have an exterior surface coating of an identical electrically conductive material such as silver, nickel or tin whereby there will be no deteriorating effect on the strands as a result of galvanic action when current is carried by the strands. Finally, the electrical conductor of the present invention includes an outer cover layer of insulating material, such as Teflon or the like.

Preferably, the electrical conductor of the present invention includes either seven strands or nineteen strands whereby such strands, when wound together tightly, will provide a generally round configuration for the electrical conductor. When seven strands are used, one of the strands is centrally located with the remaining six disposed peripherally about the central strand, and the central strand as well as two of the peripheral strands are formed substantially of the aforementioned electrically conductive grade of aluminum while the remaining four strands are formed substantially of copper.

When nineteen strands are employed, it is preferred that seven of the strands be arranged centrally and formed substantially of an electrically conductive grade of aluminum, and that the remaining twelve strands be arranged around the periphery of the centrally arranged strands and be formed substantially of copper. However, the number of aluminum and copper strands may be varied and their respective locations may be mixed throughout the electrical conductor in arbitrary fashion.

As previously mentioned, the individual strands which make up the electrical conductor of the present invention all have an exterior surface coating of an identical electrically conductive material, and this material is preferably either silver, tin, or nickel. The copper strands have a single layer of silver, tin or nickel plated thereon, and the aluminum strands have an intermediate coating of copper and an exterior coating of the same material which is plated on the copper strands. The coatings of copper, and of silver, tin or nickel, have a minimum thickness of 40 micro inches.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary elevation partly broken away of a multi-strand electrical conductor in accordance with the present invention;

FIG. 2 is a sectional view taken along line 22 in FIG. 1;

FIG. 3 is a sectional view, similar to FIG. 1, of another embodiment of the present invention;

FIG. 4 is a sectional view, similar to FIG. 1, of still another embodiment of the present invention;

FIG. 5 is a sectional view of one of the strands formed substantially of aluminum; and

FIG. 6 is a sectional view of one of the strands formed substantially of copper.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Looking now in greater detail at the accompanying drawings, FIGS. 1 and 2 illustrate an electrical conductor 10 formed according to the present invention to include nineteen individual strands. A core strand 12 is provided which has a straight longitudinal extent, and six strands 14 are closely wound in helical fashion about the core strand 12 to provide a centrally arranged cluster of seven strands having a circular crosssection as shown in FIG. 2, and the remaining twelve strands 16 are closely wound in helical fashion around the periphery of the centrally arranged cluster of strands 12, 14. In forming the electrical conductor 10, it is preferable to first wind the strands 14 about the core strand l2, and then wind the strands 16 about the strands 14 with the same direction of helical twist as strands 14. However, all'of the strands 12, 14 and 16 could be wound simultaneously, and the outer strands 16 can be wound with a helical twist opposite that of strands-14. Preferably all of the individual strands 12, 14 and 16 are 32-gauge wire, whereby the entire electrical conductor will be 20-gauge wire.

After the strands 12, 14 and 16 are wound, the entire arrangement is insulated by a suitable insulating material 18, such as Teflon or polyvinyl chloride, which forms an outer cover layer for the electrical conductor 10 having any desired thickness, such as 0.03.

. As has been previously discussed, electrical conductors used in the aerospace industry must meet rigid weight requirements as well as have a substantial current-carrying capacity, and the electrical conductor 10 of the present invention satisfies these demands by combining highly conductive copper strands with strands formed of an electrically conductive grade of aluminum to reduce significantly the overall weight of the electric conductor l0. ln the FIG. 2 embodiment of as illustrated in FIGS. 1 and 2 so as to provide the addithe present invention, the core strand l2 and the six strands l4 wound thereabout are all formed of highly conductive aluminum of a type designated in the aluminum industry as Electrically Conductive Grade. Although different compositions within this grade may be selected, it is preferred in the present invention that the particular aluminum selected have a conductivity of at least 62 percent. I

It has also been noted that the mixing of strands of different metals (i.e., copper and aluminum) within an electrical conductor will, when electric current is carried thereby,-result in a deterioration of the strands because of oxidation caused by galvanic action. Accordingly, the present invention provides for coating the exterior surface of all of the individual strands 12, 14 and 16 with an identical electrically conductive material which may be either silver, nickel or tin, whereby such oxidation will be eliminated. FIG. 6 illustrates one of the strands 12 which is formed of copper and which has an exterior coating 20 of either silver, tin or nickel plated thereon with a minimum thickness of 40 micro inches to assure that the surface of the copper 'strand 12 is entirely covered by the coating 20. The aluminum strands 16 must also be plated with either silver, tin or nickel to correspond with the copper strands 12, 14, but since these metals cannot be properly plated directly onto aluminum, the strands 16 are first plated with an intermediate coating 22 of copper having a minumum thickness of 40 micro inches, after which an outer coating 24 of silver, tin, or nickel is applied to the copper coating 22. Although silver, tin or nickel may be utilized as the outermost coating for all of the strands 12, 14 and 16, silver is usually preferred because of its high conductivity characteristics, and also because it can withstand the high temperatures encountered when Teflon, or similar materials, is applied to the electrical conductor 10 to provide the insulation 18 therefor. However, sincesilver is relatively expensive, tin may be used in place of silver where lower insulation setting temperatures are to be encountered. Nickel can be used at even higher temperatures than silver, but at some sacrifice to the overall conductivity of the electrical conductor 10.

The electrical conductor 10 of the present invention ofiers significant advantages. By employing seven aluminum strands l2, 14 in combination with twelve copper strands 16, the weight of the electrical conductor 10 is reduced by approximately 22 percent over that of a conductor composed of nineteen copper strands. However, there is very little sacrifice of current-carrying capacity, particularly since the coating of the aluminum strands 16, in addition to preventing corrosion, increases the overall current-carrying capacity of the electrical conductor 10. Thus, when silver is the coating material, the electrical conductor 10 has a current-carrying capacity which is approximately 92-94 percent of that which would be present if all of the strands were formed of copper. When nickel or tin are used as the coating material, the conductivity is about 90 percent of that of an all-copper strand conductor. Thus, a substantial reduction in weight is realized with very little loss of conductivity. I

While it is preferred that the aluminum strands 12, 14 be arranged centrally of the electrical conductor 10 tional strength of aluminum at the center of the electrical conductor 10, it is also within the scope of the present invention to mix the 12 copper strands and the seven aluminum strands throughout the electrical conductor in arbitrary fashion and to vary as desired for increased conductivity or decreased weight the number of each type of strand. Also, the total number of strands may be varied as desired. As illustrated in FIG. 4, a

- conductor 10 is formed with nine aluminum strands substantially of aluminum, the othereight aluminum strands identified by reference numeral 14, and the 10 copper strands identified by reference numeral 16. The strands are insulated by an outer cover layer 18' in the same manner as in the embodiment of F IG. 2.

Finally, FIG. 3 illustrates another embodiment of the present invention in the form of a conductor 10" which includes only seven strands rather than 19 strands. In this embodiment, there is a core strand 12" and strands 14" wound about the periphery of the core strand 12". The core strand 12" and two of the peripheral strands 14" are formed substantially of an electrically conductive grade of aluminum and the remaining four strands 14 are formed substantially of copper. The copper and aluminum strands 12', 14 are coated in the same manner as in the other embodiments, and the insulating material 18" is provided in the same manner. it will be noted, of course, that a core strand and six peripheral strands provide the electrical conductor with a circular configuration.

The present invention has been described in detail above for purposes of illustration only and is not intended to be limited by this description or otherwise to exclude any variation or equivalent arrangement that would be apparent from, or reasonably suggested by the foregoing disclosure to the skill of the art.

I claim:

l. A relatively light-weight electrical conductor comprising at least seven longitudinally extending and closely wound strands with some of said strands being formed substantially of copper and with the remainder of said strands being formed substantially of an electrically conductive grade of aluminum, each of said strands having an exterior surface coating of an identical electrically conductive material, and an outer cover layer of insulating material.

2. A light-weight electrical conductor as defined in claim 1 and further characterized in that said exterior surface coating material for said strands is silver.

3. A light-weight electrical conductor as defined in claim 1 and further characterized in that said exterior surface coating for said strands in nickel.

4. A light-weight electrical conductor as defined in claim 1 and further characterized in that said exterior surface coating for said strands is tin.

5. A light-weight electrical conductor as defined in claim 1 and further characterized in that each of said strands formed substantially of said electrically conductive grade of aluminum have an intermediate coating of copper disposed between said aluminum and said exterior surface coating, and in that said exterior surface coating is a metal taken from the group consisting of silver, nickel or tin.

6. A light-weight electrical conductor as defined in claim 1 and further characterized in that said conductor comprises nineteen strands with seven of said strands being arranged centrally of said conductor and being formed substantially of said electrically conductive grade of aluminum, and with the twelve remaining strands being disposed around the periphery of said centrally arranged strands and being formed substantially of copper.

7. A light-weight electrical conductor as defined in claim 1 and further characterized in that said strands formed substantially of copper are mixed throughout said conductor in arbitrary fashion with said strands formed substantially of aluminum.

8. A light-weight electrical conductor as defined in claim 1 and further characterized in that said conductor comprises seven strands arranged with one centrally located strand and six strands disposed around the periphery of said centrally located strand, said centrally located strand and two of said peripherally disposed strands being formed substantially of said electrically conductive grade of aluminum, and the remaining four strands being formed substantially of copper.

9. A light-weight electrical conductor as defined in claim 1 and further characterized in that said exterior surface coating for each of said strands has a minimum thickness of 40 micro inches.

(5/69) UNITED STATES PATENT OFFICE CERTIFKCATE 0F CORRECTIQN patent 3,683,103 Dated August 8, 19 72 Inventofls) John J. Mancino It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Abstract page, assignee should be Hitemp Wires, Inc., Glen Cove, New York Column 3, line 15, after "0.03" insert Column 4, line 43, after "and" insert six Column 5, line 11, delete "in" and insert therefor is Signed and sealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. Attesting Officer ROBERT GOTTSCHALK Commissioner of Patents mg? UNITED STATES PANT OFCE CERTIFICATE OF Patent No. 1 1 Dated August 1972 Inventor-(s) John J. Mancino It'is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

Abstract page, assignee should be Hitemp Wires, Inc., Glen Cove, New York Column 3, line 15, after "0.03" insert Column 4, line 43, after "and" insert six Column 5, linell', delete "in" and insert therefor is Signed and sealed this 9th day of January 1973..

, (SEAL) Attest:

EDWARD M.FLETCHER,JR. I I ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

2. A light-weight electrical conductor as defined in claim 1 and further characterized in that said exterior surface coating material for said strands is silver.
 3. A light-weight electrical conductor as defined in claim 1 and further characterized in that said exterior surface coating for said strands in nickel.
 4. A light-weight electrical conductor as defined in claim 1 and further characterized in that said exterior surface coating for said strands is tin.
 5. A light-weight electrical conductor as defined in claim 1 and further characterized in that each of said strands formed substantially of said electrically conductive grade of aluminum have an intermediate coating of copper disposed between said aluminum and said exterior surface coating, and in that said exterior surface coating is a metal taken from the group consisting of silver, nickel or tin.
 6. A light-weight electrical conductor as defined in claim 1 and further characterized in that said conDuctor comprises nineteen strands with seven of said strands being arranged centrally of said conductor and being formed substantially of said electrically conductive grade of aluminum, and with the twelve remaining strands being disposed around the periphery of said centrally arranged strands and being formed substantially of copper.
 7. A light-weight electrical conductor as defined in claim 1 and further characterized in that said strands formed substantially of copper are mixed throughout said conductor in arbitrary fashion with said strands formed substantially of aluminum.
 8. A light-weight electrical conductor as defined in claim 1 and further characterized in that said conductor comprises seven strands arranged with one centrally located strand and six strands disposed around the periphery of said centrally located strand, said centrally located strand and two of said peripherally disposed strands being formed substantially of said electrically conductive grade of aluminum, and the remaining four strands being formed substantially of copper.
 9. A light-weight electrical conductor as defined in claim 1 and further characterized in that said exterior surface coating for each of said strands has a minimum thickness of 40 micro inches. 